The present invention relates generally to an engine control method and a control apparatus therefor and, more particularly, to a multi-cylinder engine control method and an electronic control apparatus therefor, which enable combustion conditions of the respective cylinders of the multi-cylinder engine to be balanced for producing stable engine power.
Conventionally, as a well-known way of suppressing revolutional fluctuation of an engine especially at the time of idling, for example, it has been disclosed in Japanese Patent Unexamined Publication No. 58-176470, that ignition timings or fuel amounts supplied are corrected to suppress the fluctuation.
In addition, in order to balance combustion conditions of cylinders by equalizing combustion pressures of a multi-cylinder engine, various methods have been attempted. For example, so-called combustion pressure sensors are provided in the respectively cylinders so that the combustion pressures will be directly detected to effect the engine control.
However, in these conventional methods, especially in the former, after numbers of revolutions representing the engine power are detected, the ignition timings or the like of the cylinders at the succeeding procedures are suitably regulated in response to the fluctuation, so that the revolutional fluctuation is controlled to suppress vibration to some extent, but it has been almost impossible in principle to sufficiently suppress revolutional vibration caused by output unbalance of the respective cylinders of the engine, thereby resulting in discomfort to drivers or passengers who suffer from delicate vibration transmited from the vehicle body, the steering or the like.
Besides, in the latter of the above-stated conventional methods, the respective cylinders have to be provided with sensors for detecting each of the combustion pressures, which inevitably causes the cost of the control apparatus to increase, and such sensors for detecting the combustion pressures do not have enough durability, so that they have not been put into practice yet.